1. Field of the Invention
The invention relates generally to thermal interfaces; and more particularly to a kind of thermal interface which conducts heat by using carbon nanotubes.
2. Description of Related Art
Electronic components such as semiconductor chips are becoming progressively smaller, while at the same time heat dissipation requirements thereof are increasing. Commonly, a thermal interface is utilized between the electronic component and a heat sink in order to efficiently dissipate heat generated by the electronic component.
A conventional thermal interface is made by diffusing particles with a high heat conduction coefficient in a base material. The particles can be made of graphite, boron nitride, silicon oxide, alumina, silver, or other metals. However, a heat conduction coefficient of the thermal interface is now considered to be too low for many contemporary applications, because it cannot adequately meet the heat dissipation requirements of modern electronic components.
A new kind of thermal interface has recently been developed. The thermal interface is obtained by fixing carbon fibers with a polymer. The carbon fibers are distributed directionally, and each carbon fiber can provide a heat conduction path. A heat conduction coefficient of this kind of thermal interface is relatively high. However, the heat conduction coefficient of the thermal interface is inversely proportional to a thickness thereof, and the thickness is required to be greater than 40 micrometers. In other words, the heat conduction coefficient is limited to a certain value corresponding to a thickness of 40 micrometers. The value of the heat conduction coefficient cannot be increased, because the thickness cannot be reduced,
U.S. Pat. No. 6,407,922 discloses another kind of thermal interface. The thermal interface is formed by injection molding, and has a plurality of carbon nanotubes incorporated in a matrix material. A first surface of the thermal interface engages with an electronic device, and a second surface of the thermal interface engages with a heat sink. The second surface has a larger area than the first surface, so that heat can be uniformly spread over the larger second surface.
However, the thermal interface formed by injection molding is relatively thick. This increases a bulk of the thermal interface and reduces its flexibility. Furthermore, the carbon nanotubes are disposed in the matrix material randomly and multidirectionally. This means that heat does not necessarily spread uniformly through the thermal interface. In addition, the heat does not necessarily spread directly from the first surface engaged with the electronic device to the second surface engaged with the heat sink.
A new thermal interface which overcomes the above-mentioned problems is desired.